Electrosynthesis of Hydrogen Peroxide by Phase-Transfer Catalysis

Abstract

The portable electrochemical generation of hydrogen peroxide (H 2 O 2) from air and water would enable greater utilization of this versatile green oxidant in applications ranging from environmental remediation to portable sanitation. Currently, electrochemical H 2 O 2 synthesis is hampered by the lack of lowcost, non-toxic catalysts that selectively reduce O 2 to H 2 O 2 and the lack of low-energy methods for separating the produced H 2 O 2 from the electrolyte media. Herein, we show that a disulfonated anthraquinone can simultaneously catalyze the selective conversion of O 2 to H 2 O 2 and shuttle between immiscible aqueous and organic phases via ion exchange. We exploit both of these properties in a flow system to assemble an all-Earth-abundant prototype device for the continuous generation and separation of H 2 O 2 into an electrolyte-free water stream. The combination of molecular redox mediation and phase-transfer catalysis demonstrated here has broad implications for the electrochemical synthesis and isolation of value-added chemicals and fuels.

Supramolecular Tuning Enables Selective Oxygen Reduction Catalyzed by Cobalt Porphyrins for Direct Electrosynthesis of Hydrogen Peroxide

“…As such, we pursued a design strategy of site isolation, where we reasoned that supramolecular‐induced separation of molecular units could promote the 2 e − reduction pathway for direct electrosynthesis of H 2 O 2 and disfavor the 4 e − reduction to H 2 O. Indeed, complementary materials approaches for H 2 O 2 electrosynthesis that exploit site isolation include dispersed and single‐atom materials, metal organic frameworks and related reticular materials, graphite‐conjugated catalysts, and phase‐transfer catalysis . In this context, POCs are appealing supramolecular platforms that combine the synthetic tunability of molecular catalysts with the high surface area of materials catalysts, and advances continue to showcase the variety of POCs that can be synthesized .…”

Supramolecular Tuning Enables Selective Oxygen Reduction Catalyzed by Cobalt Porphyrins for Direct Electrosynthesis of Hydrogen Peroxide

“…Indeed, complementary materials approaches for H 2 O 2 electrosynthesis that exploit site isolation include dispersed and single-atom materials, [11] metal organic frameworks and related reticular materials, [12] graphite-conjugated catalysts, [13] and phase-transfer catalysis. [14] In this context, POCs are appealing supramolecular platforms that combine the synthetic tunability of molecular catalysts with the high surface area of materials catalysts, and advances continue to showcase the variety of POCs that can be synthesized. [15] Large, rigid POCs have the potential to incorporate multiple non-interacting active sites.…”

Ionicity-dependent proton-coupled electron transfer of supramolecular self-assembled electroactive heterocycles

“…6 These molecular constructs have been used in many diverse contexts, from catalysis, redox flow batteries, to dyes and antimicrobials. [7][8][9][10][11] Quinones in water possess a complex protoncoupled electron transfer process which is still challenging to fully understand despite decades of electrochemical study. This is because the aqueous redox chemistry of quinones can be affected to such a large extent by pH, both in the bulk solution and especially at the non-equilibrium conditions of the electrochemical double layer.…”

“…1, path B). [7][8][9][10][11] This has implications for the electrochemical behaviour of quinones under buffered and unbuffered conditions.…”